Electroplating apparatus with segmented anode array

ABSTRACT

An electroplating apparatus includes a reactor vessel having a segmented anode array positioned therein for effecting electroplating of an associated workpiece such as a semiconductor wafer. The anode array includes a plurality of ring-like anode segments which are preferably positioned in concentric, coplanar relationship with each other. The anode segments can be independently operated to create varying electrical potentials with the associated workpiece to promote uniform deposition of electroplated metal on the surface of the workpiece.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates generally to an electroplating apparatusfor plating of semiconductor components, and more particularly to anelectroplating apparatus, including a segmented anode array comprising aplurality of concentrically arranged anode segments which can beindependently operated to facilitate uniform deposition of electroplatedmetal on an associated workpiece.

Production of semiconductive integrated circuits and othersemiconductive devices from semiconductor wafers typically requiresformation of multiple metal layers on the wafer to electricallyinterconnect the various devices of the integrated circuit Electroplatedmetals typically include copper, nickel, gold and lead. Electroplatingis effected by initial formation of a so-called seed layer on the waferin the form of a very thin layer of metal, whereby the surface of thewafer is rendered electrically conductive. This electroconductivitypermits subsequent formation of a so-called blanket layer of the desiredmetal by electroplating in a reactor vessel. Subsequent processing, suchas chemical, mechanical planarization, removes unwanted portions of themetal blanket layer formed during electroplating, resulting in thedesired patterned metal layer in a semiconductor integrated circuit ormicro-mechanism being formed. Formation of a patterned metal layer canalso be effected by electroplating.

Subsequent to electroplating, the typical semiconductor wafer or otherworkpiece is subdivided into a number of individual semiconductorcomponents. In order to achieve the desired formation of circuitrywithin each component, while achieving the desired uniformity of platingfrom one component to the next, it is desirable to form each metal layerto a thickness which is as uniform as possible across the surface of theworkpiece. However, because each workpiece is typically joined at theperipheral portion thereof in the circuit of the electroplatingapparatus (with the workpiece typically functioning as the cathode),variations in current density across the surface of the workpiece areinevitable. In the past, efforts to promote uniformity of metaldeposition have included flow-controlling devices, such as diffusers andthe like, positioned within the electroplating reactor vessel in orderto direct and control the flow of electroplating solution against theworkpiece.

In a typical electroplating apparatus, an anode of the apparatus (eitherconsumable or non-consumable) is immersed in the electroplating solutionwithin the reactor vessel of the apparatus for creating the desiredelectrical potential at the surface of the workpiece for effecting metaldeposition. Previously employed anodes have typically been generallydisk-like in configuration, with electroplating solution directed aboutthe periphery of the anode, and through a perforate diffuser platepositioned generally above, and in spaced relationship to, the anode.The electroplating solution flows through the diffuser plate, andagainst the associated workpiece held in position above the diffuser.Uniformity of metal deposition is promoted by rotatably driving theworkpiece as metal is deposited on its surface.

The present invention is directed to an electroplating apparatus havinga segmented anode array, including a plurality of anode segments whichcan be independently operated at different electrical potentials topromote uniformity of deposition of electroplated metal on a associatedworkpiece.

BRIEF SUMMARY OF THE INVENTION

An electroplating apparatus embodying the principles of the presentinvention includes an electroplating reactor vessel which contains asegmented anode array immersed in electroplating solution held by thevessel. The anode array includes differently dimensioned anode segments,preferably comprising concentrically arranged ring-like elements, withthe anode segments being independently operable at different electricalpotentials. The flow of electroplating solution about the anode segmentsis controlled in conjunction with independent operation of the segments,with uniformity of electroplated metal deposition on the workpiece thuspromoted.

In accordance with the illustrated embodiments, the presentelectroplating apparatus includes an electroplating reactor including acup-like reactor vessel for holding electroplating solution. A segmentedanode array in accordance with the present invention is positioned inthe reactor vessel for immersion in the plating solution. Theelectroplating apparatus includes an associated rotor assembly which canbe positioned generally on top of the electroplating reactor, with therotor assembly configured to receive and retain an associated workpiecesuch as a semiconductor wafer. The rotor assembly is operable toposition the workpiece in generally confronting relationship with theanode array, with the surface of the workpiece in contact with theelectroplating solution for effecting deposition of metal on theworkpiece. The reactor vessel defines an axis, with the workpiece beingpositionable in generally transverse relationship to the axis.

The anode array comprises a plurality of anode segments having differingdimensions, with the array being operable to facilitate uniformdeposition of electroplated metal on the workpiece. In accordance withthe illustrated embodiment, the segmented anode array is positionedgenerally at the lower extent of the reactor vessel in generallyperpendicular relationship to the axis defined by the vessel. The anodearray comprises a plurality of ring-like, circular anode segmentsarranged in concentric relationship to each other about the axis. Thus,at least one of the anode segments having a relatively greater dimensionis positioned further from the axis than another one of the anodesegments having a relatively lesser dimension. In the illustratedembodiment, each of the anode segments is configured to have an annular,ring-shape, with each being generally toroidal. It is presentlypreferred that the anode segments be generally coplanar, although itwill be appreciated that the segments can be otherwise arranged.

The anode array includes a mounting base upon which the ring-like anodesegments are mounted. The present invention contemplates variousarrangements for directing and controlling flow of the associatedelectroplating solution. In particular, the mounting base can define atleast one flow passage for directing flow of electroplating solutionthrough the mounting base. In one form, a central-most one of the anodesegments defines an opening aligned with the reactor vessel axis, withthe flow passage defined by the mounting base being aligned with theopening in the central anode segment. In another embodiment, flowpassages defined by the mounting base are positioned generally betweenadjacent ones of the anode segments for directing flow of electroplatingsolution therebetween. In this embodiment, a plurality of flow passagesare provided which are arranged in a pattern of concentric circles todirect flow of electroplating solution between adjacent ones of theconcentrically arranged anode segments.

In an alternate embodiment, the mounting base includes a plurality ofdepending, flow-modulating projections, defining flow channelstherebetween, with the projections arranged generally about theperiphery of the mounting base. In the preferred form, the presentelectroplating apparatus includes a control arrangement operativelyconnected to the segmented anode array for independently operating theplurality of anode segments. This permits the segments to be operated atdifferent electrical potentials, and for differing periods of time, tofacilitate uniform deposition of electroplated metal on the associatedworkpiece. The present invention contemplates that dielectric elementscan also be positioned between at least two adjacent ones of the anodesegments for further facilitating uniform deposition of electroplatedmetal on the workpiece.

Other features and advantages of the present invention will becomereadily apparent from the following detailed description, theaccompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view, in partial cross-section, of anelectroplating reactor of an electroplating apparatus, including asegmented anode array, embodying the principles of the presentinvention;

FIG. 1 a is a diagrammatic view of a control system for the presentelectroplating apparatus;

FIG. 2 is an exploded perspective view of the segmented anode arrayillustrated in FIG. 1;

FIG. 3 is a top perspective view of the assembled anode array of FIG. 2;

FIG. 4 is a bottom perspective view of the anode array illustrated inFIG. 3;

FIG. 5 is a cross-sectional view of the anode array illustrated in thepreceding FIGURES;

FIG. 6 is an exploded perspective view of an alternative embodiment ofthe present segmented anode array;

FIG. 7 is a top perspective view of the assembled segmented anode arrayillustrated in FIG. 6;

FIG. 8 is a bottom perspective view of the anode array illustrated inFIG. 7;

FIG. 9 is a cross-sectional view of the segmented anode arrayillustrated in FIGS. 6-8;

FIG. 10 is a top perspective view of a further alternative embodiment ofthe present segmented anode array;

FIG. 11 is a bottom perspective view of the segmented anode array shownin FIG. 10;

FIG. 12 is a cross-sectional view of the segmented anode array shown inFIGS. 11 and 12;

FIG. 13 is a relatively enlarged, fragmentary cross-sectional view ofthe segmented anode array shown in FIG. 12; and

FIG. 14 is a diagrammatic view of the present electroplating apparatus,with a rotor assembly and associated reactor positioned together forworkpiece processing.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describedpresently preferred embodiments, with the understanding that the presentdisclosure is to be considered as an exemplification of the invention,and is not intended to limit the invention to the specific embodimentsillustrated.

With reference first to FIG. 1, therein is illustrated an electroplatingreactor 10 of an electroplating apparatus embodying the presentinvention. This type of electroplating apparatus is particularly suitedfor electroplating of semiconductor wafers or like workpieces, wherebyan electrically conductive seed layer of the wafer is electroplated witha metallic blanket or patterned layer.

The electroplating reactor 10 is that portion of the apparatus whichgenerally contains electroplating solution, and which directs thesolution against a generally downwardly facing surface of an associatedworkpiece, W, to be plated (see FIG. 14). To this end, the reactor 10includes a reactor vessel or cup 12 through which electroplatingsolution is circulated. Attendant to solution circulation, the solutionflows from the reactor vessel 12, over the weir-like periphery of thevessel, into a lower overflow chamber 14 of the reactor 10. Solution isdrawn from the overflow chamber typically to be replenished forre-circulation through the reactor.

Reactor 10 includes a riser tube 16, within which an inlet conduit 18 ispositioned for introduction of electroplating solution into the reactorvessel. A segmented anode array 20, embodying the principles of thepresent invention, is positioned generally at the upper extent of theinlet conduit 18 in a manner, as will be further described, whichpromotes flow of electroplating solution over and about the anode array20. During processing, a rotor assembly 22 (FIG. 14) which receives andholds a workpiece W for electroplating, is positioned in cooperativeassociation with reactor 10 such that the workpiece W is positioned ingenerally confronting relationship to the anode array 20. As will beobserved, the reactor vessel 12 defines an axis “A” (FIG. 14), with theworkpiece W positioned in generally transverse relationship to the axis.Similarly, the anode array 20 is positioned in generally transverserelationship to the axis “A”, preferably perpendicular thereto. Whilethe workpiece W may be positioned perpendicularly to the axis “A”, theillustrated arrangement positions the workpiece W at an acute angle(such as on the order of 2°) relative to the surface of theelectroplating solution within the reactor vessel 12 to facilitateventing of gas which can accumulate at the surface of the workpiece.During processing, the workpiece is rotatably driven by drive motor 24of the rotor assembly for facilitating uniformity of deposition ofelectroplated metal on the workpiece surface.

With particular reference to FIGS. 2-5, the segmented anode array 20includes a plurality of anode segments having differing dimensions, withat least one of the anode segments having a relatively greater dimensionbeing positioned further from the axis of the reactor vessel thananother one of the anode segments having a relatively lesser dimension.In particular, the anode segments comprise circular, ring-like elements,each of which is generally toroidal, and arranged in concentricrelationship with each other. As is known in the art, the anode segmentsmay be consumable, whereby metal ions of the anode segments aretransported by the electroplating solution to the electricallyconductive surface of the associated workpiece, which functions as acathode.

In this illustrated embodiment, the segmented anode array 20 includesfour (4) anode segments, respectively designated 30, 32, 34 and 36. Theanode segments are of relatively decreasing diameters, with the segmentsthus fitting one-within-the-other.

It is preferred that the anode segments be positioned in generallycoplanar relationship with each other, with the segments coaxial witheach other along axis “A”. In order to maintain the segments in thisrelative disposition, the anode array 20 includes a mounting base 40upon which each of the anode segments is mounted. The mounting base 40includes a collar portion 42 which defines a flow passage for directingflow of electroplating solution through the mounting base. In thisembodiment, the central-most one of the concentric anode segmentsdefines an opening aligned with the axis “A” of the reactor vessel, withthe flow passage defined by the collar portion of the mounting base 40being aligned with the opening defined by this central-most one 36 ofthe anode segments.

Operation of this embodiment of the present invention contemplates thatplating solution is pumped through inlet conduit 18, through the flowpassage defined by collar portion 42 of mounting base 40, and throughthe center of the anode array so that the solution impinges upon thesurface of the workpiece W. The plating rate at the surface of theworkpiece ordinarily will vary radially due to the effect of theimpinging solution on the hydrodynamic boundary layer. Compensation ofthis radial effect can be achieved by operating the anode segments atdifferent electrical potentials. Such an arrangement is diagrammaticallyillustrated in FIG. 1 a, wherein controls of the present electroplatingapparatus include suitable wiring for independently operating theplurality of segments of the anode array 20. It is contemplated that notonly can the various anode segments be operating at differing electricalpotentials, they may also be operated for differing periods of time tooptimize the uniformity of plating on the workpiece.

In addition to affecting plating uniformity by using different anodepotentials, it is within the purview of the present invention to affectuniformity by the disposition of dielectric (insulating) elementsbetween adjacent ones of the anode segments. This is illustrated inphantom line in FIG. 5, wherein dielectric elements 46 are positionedbetween each adjacent pair of the anode segments 30, 32, 34 and 36.

The geometry of the dielectric elements can be modified to provide thedesired effect on plating. Relatively tall geometries, i.e., dielectricelements which project significantly above the associated anodesegments, are believed to tend to limit interaction of adjacent ones ofthe anode segments, and can tend to collimate solution flow to theworkpiece. In contrast, shorter or perforated geometries are believed totend to increase anode segment interaction. While the illustratedembodiments of the present invention show the anode segments positionedin coplanar relationship with each other, and thus, in generallyequidistant relationship to the workpiece W, it is believed that anincrease or decrease in anode segment interaction can also be achievedby positioning the ring-like anode segments at varying distances fromthe surface of the workpiece.

Depending upon the type of electroplating process, the segments of theanode array may be either consumable, or non-consumable. For thoseapplications requiring a consumable anode, the anode segments can beformed from copper, such as phosphorized copper. In contrast,non-consumable anode segments can be formed from platinum platedtitanium.

It is contemplated that suitable mechanical fasteners (not shown) beemployed for individually securing each of the anode segments to theassociated mounting base 40. Additionally, suitable sealed wiring (notshown) is provided for individually electrically connecting each of theanode segments with associated controls of the electroplating apparatus,whereby the electrical potential created by each anode segment can beindependently varied and controlled. In this embodiment, it iscontemplated that no perforate diffuser member be employed positionedbetween the anode array 20 and the workpiece W. Solution flow rate andcurrent distribution can be controlled independently of one another tooptimize the plating process and promote uniformity of deposition ofelectroplated metal. Air bubbles introduced into the plating chamber bythe incoming plating solution are flushed past the workpiece surface,and thus will not interfere with the plating process. Venting of theworkpiece surface, by its angular disposition as discussed above, mayalso be effected. Solution flow from the center of the anode arrayinsures that the workpiece surface will be wetted from the center to theperiphery. This prevents air from being trapped at the center of theworkpiece when it first contacts the surface of the solution.

As will be appreciated, the use of a segmented anode array havingcircular anode segments is particularly suited for use with circular,disk-like wafers or like workpieces. However, it is within the purviewof the present invention that the anode array, including the anodesegments, be non-circular.

With reference now to FIGS. 6-9, therein is illustrated an alternateembodiment of the present segmented anode array. In this embodiment,elements which generally correspond to those in the above-describedembodiment are designated by like reference numerals in the one-hundredseries.

Segmented anode array 120 includes a plurality of ring-like anodesegments. In this embodiment, five (5) of the anode segments areprovided in concentric relationship with each other, including segments130, 132, 134, 136 and 138.

The anode array 120 includes a mounting base 140 having a plurality ofdivider elements 141 respectively positioned between adjacent ones ofthe circular anode segments. As in the previous embodiment, the anodesegments are positioned in coplanar relationship with each other on themounting base, and are positioned in coaxial relationship with the axis“A” of the associated reactor vessel.

In distinction from the previous embodiment, anode array 120 isconfigured such that flow of electroplating solution is directedgenerally about the periphery of the array. In particular, the mountingbase 140 includes a plurality of circumferentially spaced dependingflow-modulating projections 143 which define flow channels betweenadjacent ones of the projections. Electroplating solution is introducedinto the reactor vessel through an inlet conduit 118, which defines aplurality of flow passages 119 generally at the upper extent thereof,beneath mounting base 140, and inwardly of flow-modulating projections143. The solution then flows between the flow-modulating projections,and upwardly generally about the anode segments.

This embodiment illustrates a series of openings defined by mountingbase 140. With particular reference to FIG. 8, those series of holesaligned at 120° intervals about the base portion are configured forreceiving respective mechanical fasteners (not shown) for securing theanode segments to the mounting base. The remaining series ofradially-spaced openings defined by the mounting base are provided forsuitable electrical connection with each individual anode segment.

With reference to FIGS. 10-13, another alternate embodiment of thesegmented anode array embodying the principles of the present inventionis illustrated. Elements of this embodiment, which generally correspondto like elements in the previously described embodiment, areso-designated by like reference numerals in the two-hundred series.

Anode array 220 includes a plurality of circular, concentricallyarranged ring-like anode segments 230, 232, 234, 236 and 238. The anodesegments are positioned in coplanar relationship on a mounting base 240.Notably, this configuration of the anode array is arranged to permitflow of electroplating solution between adjacent ones of the anodesegments. To this end, the mounting base 240 defines a plurality of flowpassages 245 arranged in a pattern of concentric circles to direct flowof electroplating solution between adjacent ones of the ring-like anodesegments. An inlet conduit 218 defines a plurality of flow passages 219so that plating solution can flow from the inlet conduit through theflow passages 245. This embodiment also includes a flow passage 247defined by the mounting base 240 for directing flow through an openingdefined by the central-most one 238 of the anode segments.

From the foregoing, it will be observed that numerous modifications andvariations can be effected without departing from the true spirit andscope of the novel concept of the present invention. It will beunderstood that no limitation with respect to the specific embodimentsillustrated herein is intended or should be inferred. The disclosure isintended to cover, by the appended claims, all such modifications asfall within the scope of the claims.

1-16. (canceled)
 17. An apparatus for electrochemical processing ofmicrofeature workpieces, comprising: a reactor vessel having a centralaxis generally transverse to a plane defined by a workpiece processingposition, and the reactor vessel being configured to contain a flow ofelectrochemical processing solution; and a plurality of independentlyoperable electrodes in the reactor vessel including an innermostelectrode and a first outer electrode arranged generally transverse tothe central axis, the innermost electrode being a first conductivemember having a central opening aligned with the central axis of thereactor vessel and the outer electrode being a second conductive memberarranged concentrically with the first conductive member.
 18. Theapparatus of claim 17 wherein the first conductive member comprises afirst annular conductive member and the second conductive membercomprises a second annular conductive member.
 19. The apparatus of claim18 wherein the first annular conductive member comprises a firstconductive ring and the second annular conductive member comprises asecond conductive ring.
 20. The apparatus of claim 17 wherein the firstelectrode is separated from the second electrode by an annular wall. 21.The apparatus of claim 17 wherein the reactor vessel comprises a cuphaving a weir, and the apparatus further comprises an overflow collectorexternal to the cup configured to receive processing solution flowingover the weir.
 22. The apparatus of claim 21, further comprising adielectric separator between the innermost electrode and the first outerelectrode, and wherein the weir is at an elevation above the dielectricseparator.
 23. The apparatus of claim 17, further comprising acontroller operatively coupled to the electrodes, wherein the controlleris programmed to apply a first current to the first electrode and asecond current different than the first current to the second electrode.24. An apparatus for electrochemical processing of microelectronicworkpieces, comprising: a reactor vessel having a bottom, a sidewallprojecting from the bottom, and a generally vertical axis; and aplurality of independently operable electrodes in the reactor vesselincluding an innermost electrode being a first ring-like electrode and afirst outer electrode being a second ring-like electrode arrangedconcentrically with the first ring-like electrode about the verticalaxis.
 25. The apparatus of claim 24 wherein the first ring-likeelectrode is separated from the second ring-like electrode by an annularwall.
 26. The apparatus of claim 24 wherein the first and secondring-like electrodes are carried by an electrode mount in the reactorvessel
 27. The apparatus of claim 24 wherein the apparatus furthercomprises an overflow chamber having a floor separate from the bottom ofthe reactor vessel and an exterior wall separate from the sidewall ofthe reactor vessel, and wherein the overflow chamber is configured toreceive a flow of processing solution from the reactor vessel.
 28. Theapparatus of claim 24, further comprising a controller operativelycoupled to the ring-like electrodes, wherein the controller isprogrammed to apply a first current to the first ring-like electrode anda second current different than the first current to the secondring-like electrode.
 29. An apparatus for electrochemically processingmicroelectronic workpieces, comprising: means for holding amicroelectronic workpiece generally horizontal in a workpiece processingregion and for electrically biasing a surface of the workpiece; firstelectrically conductive means for electrically biasing an electrolyteflow at a first potential, the first electrically conductive meanshaving a central opening aligned with a central axis transverse to thecenter of the holding means; and second electrically conductive meansfor electrically biasing the electrolyte flow at a second potentialdifferent than the first potential, wherein the first electricallyconductive means is the innermost electrically conductive memberrelative to the central axis and the second electrically conductivemeans is concentric with the first electrically conductive means.